Layered actuation structures comprising artificial muscles

ABSTRACT

A layered actuation structure includes one or more actuation platforms interleaved with one or more mounting platforms to form one or more actuation cavities between platform pairs, each platform pair having an individual mounting platform and an individual actuation platform. The layered actuation structure also includes a support arm coupled to the one or more mounting platforms, an actuation arm coupled to the one or more actuation platforms, and one or more artificial muscles disposed in each of the one or more actuation cavities. The one or more artificial muscles each include an electrode pair that is actuatable between a non-actuated state and an actuated state to direct a dielectric fluid into an expandable fluid region of a housing of the artificial muscle, expanding the expandable fluid region thereby applying pressure to the one or more actuation platforms, generating translational motion of the one or more actuation platforms.

TECHNICAL FIELD

The present specification generally relates to layered actuationstructures actuated by artificial muscles.

BACKGROUND

Current robotic technologies rely on rigid components, such asservomotors to perform tasks, often in a structured environment. Thisrigidity presents limitations in many robotic applications, caused, atleast in part, by the weight-to-power ratio of servomotors and otherrigid robotics devices. The field of soft robotics improves on theselimitations by using artificial muscles and other soft actuators.Artificial muscles attempt to mimic the versatility, performance, andreliability of a biological muscle. Some artificial muscles rely onfluidic actuators, but fluidic actuators require a supply of pressurizedgas or liquid, and fluid transport must occur through systems ofchannels and tubes, limiting the speed and efficiency of the artificialmuscles. Other artificial muscles use thermally activated polymerfibers, but these are difficult to control and operate at lowefficiencies.

One particular artificial muscle design is described in the paper titled“Hydraulically amplified self-healing electrostatic actuators withmuscle-like performance” by E. Acome, S. K. Mitchell, T. G. Morrissey,M. B. Emmett, C. Benjamin, M. King, M. Radakovitz, and C. Keplinger(Science 5 Jan. 2018: Vol. 359, Issue 6371, pp. 61-65). Thesehydraulically amplified self-healing electrostatic (HASEL) actuators useelectrostatic and hydraulic forces to achieve a variety of actuationmodes. However, HASEL actuator artificial muscles have a limitedactuator power per unit volume. Furthermore, HASEL actuator artificialmuscles and other known artificial muscles are difficult to combine in asmall footprint while increasing the achievable collective force ofthese artificial muscle combinations.

Accordingly, a need exists for improved artificial muscles and actuationstructures to increase actuator power per unit volume in a smallfootprint.

SUMMARY

In one embodiment, a layered actuation structure includes one or moreactuation platforms interleaved with one or more mounting platforms toform one or more actuation cavities between platform pairs, eachplatform pair having an individual mounting platform and an individualactuation platform. The layered actuation structure also includes asupport arm coupled to the one or more mounting platforms, an actuationarm coupled to the one or more actuation platforms, and one or moreartificial muscles disposed in each of the one or more actuationcavities. The one or more artificial muscles each include a housinghaving an electrode region and an expandable fluid region, a dielectricfluid housed within the housing, and an electrode pair having a firstelectrode and a second electrode positioned in the electrode region ofthe housing, where the electrode pair is actuatable between anon-actuated state and an actuated state such that actuation from thenon-actuated state to the actuated state directs the dielectric fluidinto the expandable fluid region, expanding the expandable fluid regionthereby applying pressure to the one or more actuation platforms,generating translational motion of the one or more actuation platforms.

In another embodiment, a method for actuating a layered actuationstructure includes generating a voltage using a power supplyelectrically coupled to an electrode pair of one or more artificialmuscles where at least one of the one or more artificial muscles aredisposed in each of one or more actuation cavities formed between one ormore actuation platforms and one or more mounting platforms. The one ormore actuation platforms are interleaved with the one or more mountingplatforms to form the one or more actuation cavities between platformpairs, each platform pair having an individual mounting platform and anindividual actuation platform, a support arm is coupled to the one ormore mounting platforms and an actuation arm is coupled to the one ormore actuation platforms. Each artificial muscle includes a housinghaving an electrode region and an expandable fluid region, a dielectricfluid is housed within the housing, and the electrode pair includes afirst electrode and a second electrode and is positioned in theelectrode region of the housing. The method further includes applyingthe voltage to the electrode pair of at least one artificial muscledisposed in at least one of the one or more actuation cavities, therebyactuating the electrode pair of the at least one artificial muscle froma non-actuated state to an actuated state such that the dielectric fluidis directed into the expandable fluid region of the at least oneartificial muscle and expands the expandable fluid region therebyapplying pressure to at least one actuation platform, generatingtranslational motion of the one or more actuation platforms.

These and additional features provided by the embodiments describedherein will be more fully understood in view of the following detaileddescription, in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments set forth in the drawings are illustrative and exemplaryin nature and not intended to limit the subject matter defined by theclaims. The following detailed description of the illustrativeembodiments can be understood when read in conjunction with thefollowing drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 schematically depicts an exploded view of an illustrativeartificial muscle, according to one or more embodiments shown anddescribed herein;

FIG. 2 schematically depicts a top view of the artificial muscle of FIG.1, according to one or more embodiments shown and described herein;

FIG. 3A schematically depicts a cross-sectional view of the artificialmuscle of FIGS. 1 and 2 taken along line 3-3 in FIG. 2 in a non-actuatedstate, according to one or more embodiments shown and described herein;

FIG. 3B schematically depicts a cross-sectional view of the artificialmuscle of FIG. 1 taken along line 3-3 in FIG. 2 in an actuated state,according to one or more embodiments shown and described herein;

FIG. 4A schematically depicts a cross-sectional view of anotherillustrative artificial muscle in a non-actuated state, according to oneor more embodiments shown and described herein;

FIG. 4B schematically depicts a cross-sectional view of the artificialmuscle of FIG. 4A in an actuated state, according to one or moreembodiments shown and described herein;

FIG. 5A schematically depicts a top view of an example artificial musclestack comprising a plurality of artificial muscle layers positioned in acoaxial alignment, according to one or more embodiments shown anddescribed herein;

FIG. 5B schematically depicts a side view of the artificial muscle stackof FIG. 5A along line 5B-5B in an unactuated state, according to one ormore embodiments shown and described herein;

FIG. 5C schematically depicts a side view of the artificial muscle stackof FIG. 5A along line 5B-5B in an actuated state, according to one ormore embodiments shown and described herein;

FIG. 6A schematically depicts a top view of an example artificial musclestack comprising a plurality of artificial muscle layers positioned inalternatingly offset arrangement, according to one or more embodimentsshown and described herein;

FIG. 6B schematically depicts a side view of the artificial muscle stackof FIG. 6A along line 6B-6B in an unactuated state, according to one ormore embodiments shown and described herein;

FIG. 6C schematically depicts a side view of the artificial muscle stackof FIG. 6A along line 6B-6B in an actuated state, according to one ormore embodiments shown and described herein;

FIG. 6D schematically depicts a side view of the artificial muscle stackof FIG. 6A along line 6D-6D in an unactuated state, according to one ormore embodiments shown and described herein;

FIG. 6E schematically depicts a side view of the artificial muscle stackof FIG. 6A along line 6D-6D in an unactuated state, according to one ormore embodiments shown and described herein;

FIG. 7 schematically depicts a top view of an example artificial musclestack comprising a plurality of artificial muscle layers positioned inalternatingly offset arrangement with the addition of perimeterartificial muscles, according to one or more embodiments shown anddescribed herein;

FIG. 8A schematically depicts a cross section of layered actuationstructure comprising artificial muscles in a non-actuated state,according to one or more embodiments shown and described herein;

FIG. 8B schematically depicted the layered actuation structure of FIG.8A in which the artificial muscles are in an actuated state, accordingto one or more embodiments shown and described herein;

FIG. 9 schematically depicts an example layered actuation structure,according to one or more embodiments shown and described herein;

FIG. 10 schematically depicts another example layered actuationstructure, according to one or more embodiments shown and describedherein; and

FIG. 11 schematically depicts an actuation system for operating theartificial muscles of the layered actuation structures of FIGS. 8A-10,according to one or more embodiments shown and described herein.

DETAILED DESCRIPTION

Embodiments described herein are directed to a layered actuationstructure having one or more actuation platforms interleaved with one ormore mounting platforms. Adjacent individual actuation platforms andmounting platforms form platform pairs having an actuation cavitybetween the actuation platform and the mounting platform. Platform pairsare connected to one another using platform linking arms. Artificialmuscles are disposed in the actuation cavity of each platform pair andare expandable on demand to selectively raise the actuation platforms.In particular, the one or more artificial muscles each include anelectrode pair that may be drawn together by application of a voltage,thereby pushing dielectric fluid into an expandable fluid region,expanding the expandable fluid region, raising a portion of theartificial muscle on demand. Expansion of the expandable fluid regionsapply pressure to the one or more actuation platforms, generatingtranslational motion of the one or more actuation platforms.

In operation, the translational motion of each of the one or moreactuation platforms generates an additive force that may be increased byadding additional platform pairs to the layered actuation structure. Incontrast, vertically stacking artificial muscles (i.e., separate from alayered actuation structure) generates an additive displacement that maybe increased by adding additional artificial muscles but does notgenerate an additive force. Furthermore, increasing the number orartificial muscles laterally arranged side-by-side increases thecollectively achievable maximum force, but requires an ever increasinglateral footprint to increase the collective maximum force, diminishingthe practicality of such an arrangement. In the embodiments describedherein, each additional platform pair of the layered actuation structureincreases the achievable maximum force without increasing the totaldisplacement that occurs during actuation. Thus, the layered actuationstructure is useful in small footprint applications, particular smalllateral footprint applications. Furthermore, the artificial muscles ineach actuation cavity may be arranged in an alternatingly offsetarrangement to facilitate maximum packing of artificial muscles in eachactuation cavity to further increase the maximum force achievable by thelayered actuation structure while retaining a small footprint. Variousembodiments of the layered actuation structure are described in moredetail herein. Whenever possible, the same reference numerals will beused throughout the drawings to refer to the same or like parts.

Referring now to FIGS. 1 and 2, an example artificial muscle 100 thatmay be disposed in an artificial muscle stack 201, 301, 301′ (FIGS.5A-7) and in a layered actuation structure 500 (FIGS. 8A-10) isschematically depicted. The artificial muscle 100 comprises a housing110, the electrode pair 104, including a first electrode 106 and asecond electrode 108, fixed to opposite surfaces of the housing 110, afirst electrical insulator layer 111 fixed to the first electrode 106,and a second electrical insulator layer 112 fixed to the secondelectrode 108. In some embodiments, the housing 110 is a one-piecemonolithic layer including a pair of opposite inner surfaces, such as afirst inner surface 114 and a second inner surface 116, and a pair ofopposite outer surfaces, such as a first outer surface 118 and a secondouter surface 120. In some embodiments, the first inner surface 114 andthe second inner surface 116 of the housing 110 are heat-sealable. Inother embodiments, the housing 110 may be a pair of individuallyfabricated film layers, such as a first film layer 122 and a second filmlayer 124. Thus, the first film layer 122 includes the first innersurface 114 and the first outer surface 118, and the second film layer124 includes the second inner surface 116 and the second outer surface120.

While the embodiments described herein primarily refer to the housing110 as comprising the first film layer 122 and the second film layer124, as opposed to the one-piece housing, it should be understood thateither arrangement is contemplated. In some embodiments, the first filmlayer 122 and the second film layer 124 generally include the samestructure and composition. For example, in some embodiments, the firstfilm layer 122 and the second film layer 124 each comprises biaxiallyoriented polypropylene.

The first electrode 106 and the second electrode 108 are each positionedbetween the first film layer 122 and the second film layer 124. In someembodiments, the first electrode 106 and the second electrode 108 areeach aluminum-coated polyester such as, for example, Mylar®. Inaddition, one of the first electrode 106 and the second electrode 108 isa negatively charged electrode and the other of the first electrode 106and the second electrode 108 is a positively charged electrode. Forpurposes discussed herein, either electrode 106, 108 may be positivelycharged so long as the other electrode 106, 108 of the artificial muscle100 is negatively charged.

The first electrode 106 has a film-facing surface 126 and an oppositeinner surface 128. The first electrode 106 is positioned against thefirst film layer 122, specifically, the first inner surface 114 of thefirst film layer 122. In addition, the first electrode 106 includes afirst terminal 130 extending from the first electrode 106 past an edgeof the first film layer 122 such that the first terminal 130 can beconnected to a power supply to actuate the first electrode 106.Specifically, the terminal is coupled, either directly or in series, toa power supply and a controller of an actuation system 400, as shown inFIG. 7. Similarly, the second electrode 108 has a film-facing surface148 and an opposite inner surface 150. The second electrode 108 ispositioned against the second film layer 124, specifically, the secondinner surface 116 of the second film layer 124. The second electrode 108includes a second terminal 152 extending from the second electrode 108past an edge of the second film layer 124 such that the second terminal152 can be connected to a power supply and a controller of the actuationsystem 400 to actuate the second electrode 108.

The first electrode 106 includes two or more tab portions 132 and two ormore bridge portions 140. Each bridge portion 140 is positioned betweenadjacent tab portions 132, interconnecting these adjacent tab portions132. Each tab portion 132 has a first end 134 extending radially from acenter axis C of the first electrode 106 to an opposite second end 136of the tab portion 132, where the second end 136 defines a portion of anouter perimeter 138 of the first electrode 106. Each bridge portion 140has a first end 142 extending radially from the center axis C of thefirst electrode 106 to an opposite second end 144 of the bridge portion140 defining another portion of the outer perimeter 138 of the firstelectrode 106. Each tab portion 132 has a tab length L1 and each bridgeportion 140 has a bridge length L2 extending in a radial direction fromthe center axis C of the first electrode 106. The tab length L1 is adistance from the first end 134 to the second end 136 of the tab portion132 and the bridge length L2 is a distance from the first end 142 to thesecond end 144 of the bridge portion 140. The tab length L1 of each tabportion 132 is longer than the bridge length L2 of each bridge portion140. In some embodiments, the bridge length L2 is 20% to 50% of the tablength L1, such as 30% to 40% of the tab length L1.

In some embodiments, the two or more tab portions 132 are arranged inone or more pairs of tab portions 132. Each pair of tab portions 132includes two tab portions 132 arranged diametrically opposed to oneanother. In some embodiments, the first electrode 106 may include onlytwo tab portions 132 positioned on opposite sides or ends of the firstelectrode 106. In some embodiments, as shown in FIGS. 1 and 2, the firstelectrode 106 includes four tab portions 132 and four bridge portions140 interconnecting adjacent tab portions 132. In this embodiment, thefour tab portion 132 are arranged as two pairs of tab portions 132diametrically opposed to one another. Furthermore, as shown, the firstterminal 130 extends from the second end 136 of one of the tab portions132 and is integrally formed therewith.

Like the first electrode 106, the second electrode 108 includes at leasta pair of tab portions 154 and two or more bridge portions 162. Eachbridge portion 162 is positioned between adjacent tab portions 154,interconnecting these adjacent tab portions 154. Each tab portion 154has a first end 156 extending radially from a center axis C of thesecond electrode 108 to an opposite second end 158 of the tab portion154, where the second end 158 defines a portion of an outer perimeter160 of the second electrode 108. Due to the first electrode 106 and thesecond electrode 108 being coaxial with one another, the center axis Cof the first electrode 106 and the second electrode 108 are the same.Each bridge portion 162 has a first end 164 extending radially from thecenter axis C of the second electrode to an opposite second end 166 ofthe bridge portion 162 defining another portion of the outer perimeter160 of the second electrode 108. Each tab portion 154 has a tab lengthL3 and each bridge portion 162 has a bridge length L4 extending in aradial direction from the center axis C of the second electrode 108. Thetab length L3 is a distance from the first end 156 to the second end 158of the tab portion 154 and the bridge length L4 is a distance from thefirst end 164 to the second end 166 of the bridge portion 162. The tablength L3 is longer than the bridge length L4 of each bridge portion162. In some embodiments, the bridge length L4 is 20% to 50% of the tablength L3, such as 30% to 40% of the tab length L3.

In some embodiments, the two or more tab portions 154 are arranged inone or more pairs of tab portions 154. Each pair of tab portions 154includes two tab portions 154 arranged diametrically opposed to oneanother. In some embodiments, the second electrode 108 may include onlytwo tab portions 154 positioned on opposite sides or ends of the firstelectrode 106. In some embodiments, as shown in FIGS. 1 and 2, thesecond electrode 108 includes four tab portions 154 and four bridgeportions 162 interconnecting adjacent tab portions 154. In thisembodiment, the four tab portions 154 are arranged as two pairs of tabportions 154 diametrically opposed to one another. Furthermore, asshown, the second terminal 152 extends from the second end 158 of one ofthe tab portions 154 and is integrally formed therewith.

Referring now to FIGS. 1-4B, at least one of the first electrode 106 andthe second electrode 108 has a central opening formed therein betweenthe first end 134 of the tab portions 132 and the first end 142 of thebridge portions 140. In FIGS. 3A and 3B, the first electrode 106 has acentral opening 146. However, it should be understood that the firstelectrode 106 does not need to include the central opening 146 when acentral opening is provided within the second electrode 108, as shown inFIGS. 4A and 4B. Alternatively, the second electrode 108 does not needto include the central opening when the central opening 146 is providedwithin the first electrode 106. Referring still to FIGS. 1-4B, the firstelectrical insulator layer 111 and the second electrical insulator layer112 have a geometry generally corresponding to the first electrode 106and the second electrode 108, respectively. Thus, the first electricalinsulator layer 111 and the second electrical insulator layer 112 eachhave tab portions 170, 172 and bridge portions 174, 176 corresponding tolike portions on the first electrode 106 and the second electrode 108.Further, the first electrical insulator layer 111 and the secondelectrical insulator layer 112 each have an outer perimeter 178, 180corresponding to the outer perimeter 138 of the first electrode 106 andthe outer perimeter 160 of the second electrode 108, respectively, whenpositioned thereon.

It should be appreciated that, in some embodiments, the first electricalinsulator layer 111 and the second electrical insulator layer 112generally include the same structure and composition. As such, in someembodiments, the first electrical insulator layer 111 and the secondelectrical insulator layer 112 each include an adhesive surface 182, 184and an opposite non-sealable surface 186, 188, respectively. Thus, insome embodiments, the first electrical insulator layer 111 and thesecond electrical insulator layer 112 are each a polymer tape adhered tothe inner surface 128 of the first electrode 106 and the inner surface150 of the second electrode 108, respectively.

Referring now to FIGS. 2-4B, the artificial muscle 100 is shown in itsassembled form with the first terminal 130 of the first electrode 106and the second terminal 152 of the second electrode 108 extending pastan outer perimeter of the housing 110, i.e., the first film layer 122and the second film layer 124. As shown in FIG. 2, the second electrode108 is stacked on top of the first electrode 106 and, therefore, thefirst electrode 106, the first film layer 122, and the second film layer124 are not shown. In its assembled form, the first electrode 106, thesecond electrode 108, the first electrical insulator layer 111, and thesecond electrical insulator layer 112 are sandwiched between the firstfilm layer 122 and the second film layer 124. The first film layer 122is partially sealed to the second film layer 124 at an area surroundingthe outer perimeter 138 of the first electrode 106 and the outerperimeter 160 of the second electrode 108. In some embodiments, thefirst film layer 122 is heat-sealed to the second film layer 124.Specifically, in some embodiments, the first film layer 122 is sealed tothe second film layer 124 to define a sealed portion 190 surrounding thefirst electrode 106 and the second electrode 108. The first film layer122 and the second film layer 124 may be sealed in any suitable manner,such as using an adhesive, heat sealing, or the like.

The first electrode 106, the second electrode 108, the first electricalinsulator layer 111, and the second electrical insulator layer 112provide a barrier that prevents the first film layer 122 from sealing tothe second film layer 124 forming an unsealed portion 192. The unsealedportion 192 of the housing 110 includes the electrode region 194, inwhich the electrode pair 104 is provided, and the expandable fluidregion 196, which is surrounded by the electrode region 194. The centralopenings 146, 168 of the first electrode 106 and the second electrode108 form the expandable fluid region 196 and are arranged to be axiallystacked on one another. Although not shown, the housing 110 may be cutto conform to the geometry of the electrode pair 104 and reduce the sizeof the artificial muscle 100, namely, the size of the sealed portion190.

A dielectric fluid 198 is provided within the unsealed portion 192 andflows freely between the first electrode 106 and the second electrode108. A “dielectric” fluid as used herein is a medium or material thattransmits electrical force without conduction and as such has lowelectrical conductivity. Some non-limiting example dielectric fluidsinclude perfluoroalkanes, transformer oils, and deionized water. Itshould be appreciated that the dielectric fluid 198 may be injected intothe unsealed portion 192 of the artificial muscle 100 using a needle orother suitable injection device.

Referring now to FIGS. 3A and 3B, the artificial muscle 100 isactuatable between a non-actuated state and an actuated state. In thenon-actuated state, as shown in FIG. 3A, the first electrode 106 and thesecond electrode 108 are partially spaced apart from one anotherproximate the central openings 146, 168 thereof and the first end 134,156 of the tab portions 132, 154. The second end 136, 158 of the tabportions 132, 154 remain in position relative to one another due to thehousing 110 being sealed at the outer perimeter 138 of the firstelectrode 106 and the outer perimeter 160 of the second electrode 108.In the actuated state, as shown in FIG. 3B, the first electrode 106 andthe second electrode 108 are brought into contact with and orientedparallel to one another to force the dielectric fluid 198 into theexpandable fluid region 196. This causes the dielectric fluid 198 toflow through the central openings 146, 168 of the first electrode 106and the second electrode 108 and inflate the expandable fluid region196.

Referring now to FIG. 3A, the artificial muscle 100 is shown in thenon-actuated state. The electrode pair 104 is provided within theelectrode region 194 of the unsealed portion 192 of the housing 110. Thecentral opening 146 of the first electrode 106 and the central opening168 of the second electrode 108 are coaxially aligned within theexpandable fluid region 196. In the non-actuated state, the firstelectrode 106 and the second electrode 108 are partially spaced apartfrom and non-parallel to one another. Due to the first film layer 122being sealed to the second film layer 124 around the electrode pair 104,the second end 136, 158 of the tab portions 132, 154 are brought intocontact with one another. Thus, dielectric fluid 198 is provided betweenthe first electrode 106 and the second electrode 108, thereby separatingthe first end 134, 156 of the tab portions 132, 154 proximate theexpandable fluid region 196. Stated another way, a distance between thefirst end 134 of the tab portion 132 of the first electrode 106 and thefirst end 156 of the tab portion 154 of the second electrode 108 isgreater than a distance between the second end 136 of the tab portion132 of the first electrode 106 and the second end 158 of the tab portion154 of the second electrode 108. This results in the electrode pair 104zippering toward the expandable fluid region 196 when actuated. In someembodiments, the first electrode 106 and the second electrode 108 may beflexible. Thus, as shown in FIG. 3A, the first electrode 106 and thesecond electrode 108 are convex such that the second ends 136, 158 ofthe tab portions 132, 154 thereof may remain close to one another, butspaced apart from one another proximate the central openings 146, 168.In the non-actuated state, the expandable fluid region 196 has a firstheight H1.

When actuated, as shown in FIG. 3B, the first electrode 106 and thesecond electrode 108 zipper toward one another from the second ends 144,158 of the tab portions 132, 154 thereof, thereby pushing the dielectricfluid 198 into the expandable fluid region 196. As shown, when in theactuated state, the first electrode 106 and the second electrode 108 areparallel to one another. In the actuated state, the dielectric fluid 198flows into the expandable fluid region 196 to inflate the expandablefluid region 196. As such, the first film layer 122 and the second filmlayer 124 expand in opposite directions. In the actuated state, theexpandable fluid region 196 has a second height H2, which is greaterthan the first height H1 of the expandable fluid region 196 when in thenon-actuated state. Although not shown, it should be noted that theelectrode pair 104 may be partially actuated to a position between thenon-actuated state and the actuated state. This would allow for partialinflation of the expandable fluid region 196 and adjustments whennecessary.

In order to move the first electrode 106 and the second electrode 108toward one another, a voltage is applied by a power supply (such aspower supply 48 of FIG. 7). In some embodiments, a voltage of up to 10kV may be provided from the power supply to induce an electric fieldthrough the dielectric fluid 198. The resulting attraction between thefirst electrode 106 and the second electrode 108 pushes the dielectricfluid 198 into the expandable fluid region 196. Pressure from thedielectric fluid 198 within the expandable fluid region 196 causes thefirst film layer 122 and the first electrical insulator layer 111 todeform in a first axial direction along the center axis C of the firstelectrode 106 and causes the second film layer 124 and the secondelectrical insulator layer 112 to deform in an opposite second axialdirection along the center axis C of the second electrode 108. Once thevoltage being supplied to the first electrode 106 and the secondelectrode 108 is discontinued, the first electrode 106 and the secondelectrode 108 return to their initial, non-parallel position in thenon-actuated state. In operation, voltage may be applied to one ormultiple artificial muscles 100 of the artificial muscle stacks 201,301, 301′ of FIGS. 5A-7 and the layered actuation structure 500 (FIGS.8A-10) to collectively and/or selectively actuate the artificial muscles100 of the artificial muscle stacks 201, 301, 301′ and the layeredactuation structure 500.

It should be appreciated that the present embodiments of the artificialmuscle 100 disclosed herein, specifically, the tab portions 132, 154with the interconnecting bridge portions 174, 176, provide a number ofimprovements over actuators that do not include the tab portions 132,154, such as hydraulically amplified self-healing electrostatic (HASEL)actuators described in the paper titled “Hydraulically amplifiedself-healing electrostatic actuators with muscle-like performance” by E.Acome, S. K. Mitchell, T. G. Morrissey, M. B. Emmett, C. Benjamin, M.King, M. Radakovitz, and C. Keplinger (Science 5 Jan. 2018: Vol. 359,Issue 6371, pp. 61-65). Embodiments of the artificial muscle 100including two pairs of tab portions 132, 154 on each of the firstelectrode 106 and the second electrode 108, respectively, reduces theoverall mass and thickness of the artificial muscle 100, reduces theamount of voltage required during actuation, and decreases the totalvolume of the artificial muscle 101 without reducing the amount ofresulting force after actuation as compared to known HASEL actuatorsincluding donut-shaped electrodes having a uniform, radially-extendingwidth. More particularly, the tab portions 132, 154 of the artificialmuscle 100 provide zipping fronts that result in increased actuationpower by providing localized and uniform hydraulic actuation of theartificial muscle 100 compared to HASEL actuators including donut-shapedelectrodes. Specifically, one pair of tab portions 132, 154 providestwice the amount of actuator power per unit volume as compared todonut-shaped HASEL actuators, while two pairs of tab portions 132, 154provide four times the amount of actuator power per unit volume. Thebridge portions 174, 176 interconnecting the tab portions 132, 154 alsolimit buckling of the tab portions 132, 154 by maintaining the distancebetween adjacent tab portions 132, 154 during actuation. Because thebridge portions 174, 176 are integrally formed with the tab portions132, 154, the bridge portions 174, 176 also prevent leakage between thetab portions 132, 154 by eliminating attachment locations that providean increased risk of rupturing.

In operation, when the artificial muscle 100 is actuated, expansion ofthe expandable fluid region 196 produces a force of 3 Newton-millimeters(N·mm) per cubic centimeter (cm³) of actuator volume or greater, such as4 N·mm per cm³ or greater, 5 N·mm per cm³ or greater, 6 N·mm per cm³ orgreater, 7 N·mm per cm³ or greater, 8 N·mm per cm³ or greater, or thelike. In one example, when the artificial muscle 100 is actuated by avoltage of 9.5 kilovolts (kV), the artificial muscle 100 provides aresulting force of 5 N. In another example, when the artificial muscle100 is actuated by a voltage of 10 kV the artificial muscle 100 provides440% strain under a 500 gram load.

Moreover, the size of the first electrode 106 and the second electrode108 is proportional to the amount of displacement of the dielectricfluid 198. Therefore, when greater displacement within the expandablefluid region 196 is desired, the size of the electrode pair 104 isincreased relative to the size of the expandable fluid region 196. Itshould be appreciated that the size of the expandable fluid region 196is defined by the central openings 146, 168 in the first electrode 106and the second electrode 108. Thus, the degree of displacement withinthe expandable fluid region 196 may alternatively, or in addition, becontrolled by increasing or reducing the size of the central openings146, 168.

As shown in FIGS. 4A and 4B, another embodiment of an artificial muscle100′ is illustrated. The artificial muscle 100′ is substantially similarto the artificial muscle 100. As such, like structure is indicated withlike reference numerals. However, as shown, the first electrode 106 doesnot include a central opening. Thus, only the second electrode 108includes the central opening 168 formed therein. As shown in FIG. 8, theartificial muscle 100′ is in the non-actuated state with the firstelectrode 106 being planar and the second electrode 108 being convexrelative to the first electrode 106. In the non-actuated state, theexpandable fluid region 196 has a first height H3. In the actuatedstate, as shown in FIG. 4B, the expandable fluid region 196 has a secondheight H4, which is greater than the first height H3. It should beappreciated that by providing the central opening 168 only in the secondelectrode 108 as opposed to both the first electrode 106 and the secondelectrode 108, the total deformation may be formed on one side of theartificial muscle 100′. In addition, because the total deformation isformed on only one side of the artificial muscle 100′, the second heightH4 of the expandable fluid region 196 of the artificial muscle 100′extends further from a longitudinal axis perpendicular to the centralaxis C of the artificial muscle 100′ than the second height H2 of theexpandable fluid region 196 of the artificial muscle 100 when all otherdimensions, orientations, and volume of dielectric fluid are the same.

Referring now to FIGS. 5A-7, artificial muscle stacks 201, 301, 301′ aredepicted. In FIGS. 5A-7, each artificial muscle stack 201, 301, 301′comprises a plurality of artificial muscle layers 210, 310 and each ofthe plurality of artificial muscle layers 210, 310 comprise one of moreartificial muscles 100. In some embodiments, the plurality of artificialmuscle layers may alternatively or additionally comprise the artificialmuscles 100′ of FIGS. 4A and 4B). In operation, artificial muscle stacks201, 301, 301′ generate more actuation force than a single artificialmuscle 100. FIGS. 5A-7 depict a few different stack arrangements thatmay be used to generate increased actuation force.

The artificial muscle stack 201 of FIGS. 5A-5C comprises a plurality ofartificial muscle layers 210 disposed in coaxial alignment, such thatexpandable fluid regions 196 of each individual artificial muscle 100 ofan individual artificial muscle layer 210 is in coaxial alignment withan individual artificial muscle 100 of each of the other individualartificial muscle layers 210. As shown in the side view of FIGS. 5B and5C, the artificial muscle stack 201 comprises three artificial musclelayers 210A-210C. It should be understood that any number of artificialmuscle layers 210 is contemplated. FIG. 5B depicts the artificial musclestack 201 in an unactuated state and FIG. 5C depicts the artificialmuscle stack 201 in an actuated state. In each layer of the artificialmuscle stack 201, individual artificial muscles 100 do not overlap.Further, artificial muscles 100 in adjacent artificial muscle layers 210may be adhered or sewn together to help stabilize their positioning.Thus, while the artificial muscle stack 201 of FIGS. 5A-5B may generatea collective actuation force, the coaxial alignment of the individualartificial muscles 100 of each artificial muscle layer 210 creates alarge footprint. To reduce the footprint of the arrangement ofartificial muscles, the artificial muscle stack 301 depicted in FIGS.6A-6E may be implemented.

The artificial muscle stack 301 of FIGS. 6A-6E, comprises a plurality ofartificial muscle layers 310 arranged in an alternatingly offsetarrangement. The artificial muscle stack 301 comprises four artificialmuscle layers 310, a first artificial muscle layer 310A, a secondartificial muscle layer 310B, a third artificial muscle layer 310C, anda fourth artificial muscle layer 310D. FIG. 6A is a top view of theartificial muscle stack 301 and FIGS. 6B-6E are side views of theartificial muscle stack 301. FIGS. 6B and 6C show a side view of theartificial muscle stack 301 along line 6B-6B in an unactuated state(FIG. 6B) and in an actuated state (FIG. 6C). FIGS. 6D and 6E show aside view of the artificial muscle stack 301 along line 6D-6D in anunactuated state (FIG. 6D) and in an actuated state (FIG. 6E). Line6B-6B is orthogonal to line 6D-6D and thus FIGS. 6B and 6C show adifferent side of the artificial muscle stack 301 than FIGS. 6D and 6Eand the side shown by FIGS. 6B and 6C is orthogonal to the side shown byFIGS. 6D and 6E.

Each artificial muscle layer 310 comprises one or more artificialmuscles 100, for example, a plurality of artificial muscles 100. Forexample, in FIG. 6A, a first artificial muscle 100A is illustrative ofthe artificial muscles 100 of the artificial muscle stack 301. It shouldbe understood that embodiments are contemplated in which some of theartificial muscle layers 310 of the artificial muscle stack 301comprises a single artificial muscle 100. Further, artificial muscles100 in adjacent artificial muscle layers 310 may be adhered or sewntogether to help stabilize their positioning. In the alternating offsetarrangement of the artificial muscle stack 301 depicted in FIGS. 6A-6E,the plurality of artificial muscle layers 310 are arranged such thateach expandable fluid region 196 of the housing 110 of the one or moreartificial muscles 100 of each artificial muscle layer 310 overlaps atleast one tab portion 132, 154 of one or more artificial muscles 100 ofan adjacent artificial muscle layer 310. In other words, each expandablefluid region 196 of the housing 110 of the one or more artificialmuscles 100 of each artificial muscle layer 310 overlaps the electroderegion 194 of the housing 110 of one or more artificial muscles 100 ofan adjacent artificial muscle layer 310. In some embodiments, anindividual tab portion 132, 154 of one artificial muscle 100 may overlapthe expandable fluid region 196 of an artificial muscle 100 in anadjacent artificial muscle layer 310 such that the second end 136, 158of the individual tab portion 132, 154 terminates at or near the centeraxis C of the expandable fluid region 196 of the artificial muscle 100in the adjacent muscle layer 310. Thus, some of the expandable fluidregions 196 may be overlapped by two tab portions 132, 154, each from adifferent artificial muscle 100, on one or both sides of the expandablefluid region 196. The tab portions 154 of the second electrode 108 ofthe electrode pair 104 are shown in FIG. 6A but it should be understoodthat the electrode pair 104 also includes the first electrode 106 withtab portions 132.

To illustrate the alternatingly offset arrangement of the artificialmuscle stack 301 in FIGS. 6A-6E, relative line thickness of theartificial muscles 100 of each artificial muscle layer 310 is used toillustrate a relative spatial positioning of the respective artificialmuscle layers 310. For example, in FIG. 6A, the first artificial musclelayer 310A is the top layer, so the artificial muscles 100 of the firstartificial muscle layer 310A are depicted with the widest line thicknessof the plurality of artificial muscle layers 310. Similarly, in FIG. 6A,the fourth artificial muscle layer 310D is the bottom layer, so theartificial muscles 100 of the fourth artificial muscle layer 310D aredepicted with the narrowest line thickness of the plurality artificialmuscle layers 310.

In the alternatingly offset arrangement of the artificial muscle stack301, adjacent artificial muscle layers 310 of the artificial musclestack 301 are offset from one another along one or more tab axes, suchas a first tab axis 10 or a second tab axis 12. Each tab axis extendsfrom a center axis C of the expandable fluid region 196 of an individualartificial muscle 100 of the plurality of artificial muscle layers 310to an end (i.e., the second end 136, 158) of at least one of the tabportions 132, 154 of the individual artificial muscle 100 of theplurality of artificial muscle layers 310. As the embodiments of theartificial muscles 100 of the artificial muscle stack 301 depicted inFIGS. 6A-6E each comprise four tab portions 132, 154 arranged indiametrically opposed pairs, the first tab axis 10 is orthogonal thesecond tab axis 12. While the artificial muscles 100 of the artificialmuscle stack 310 comprise four tab portions 132, 154 (i.e., eachelectrode of the electrode pair 104 of each artificial muscles 100comprises four tab portions 132, 154), it should be understood thatembodiments are contemplated with artificial muscles 100 comprising moreor less than four tab portions 132, 154. These embodiments may comprisemore than two tab axis, such as in an embodiment with three tab portionsper electrode, five tab portions per electrode, or six tab portions perelectrode, or just a single tab axis, such as embodiments comprising asingle pair of diametrically opposed tab portions. Moreover, it shouldbe understood that embodiments are contemplated in which otherartificial muscle designs are arranged in an alternatingly offsetarrangement, for example, triangular or rectangular artificial muscles.

Referring still to FIGS. 6A-6E, embodiments of the artificial musclestack 301 comprising at least three artificial muscle layers 310 includeat least one inner artificial muscle layer, which is an artificialmuscle layer 310 adjacent two other artificial muscle layers 310. Inthese embodiments, each inner artificial muscle layer is offset a firstadjacent artificial muscle layer along a first tab axis 10 and offset asecond adjacent artificial muscle layer along a second tab axis 12. Thismulti-axis offset is depicted in the side views of FIGS. 6B-6E by alateral shift, which shows offset along one tab axis, and by a relativeline thickness, which shows offset along the other tab axis. In FIGS. 6Band 6C, offsets between artificial muscle layers 310 along the secondtab axis 12 are shown by a lateral shift and offsets between adjacentartificial muscle layers 310 along the first tab axis 10 are shown by arelative line thickness. In particular, a wider line thickness in FIGS.6B and 6C denotes artificial muscle layers 310 shifted along the firsttab axis 10 into the foreground (i.e., out of the page) and a narrowerline thickness in FIGS. 6B and 6C denotes artificial muscle layers 310shifted along the first tab axis 10 into the background (i.e., into thepage). In FIGS. 6D and 6E, offsets between artificial muscle layers 310along the first tab axis 10 are shown by a lateral shift and offsetsbetween adjacent artificial muscle layers 310 along the second tab axis12 are shown by a relative line thickness. In particular, a wider linethickness in FIGS. 6D and 6E denotes artificial muscle layers 310shifted along the second tab axis 12 into the foreground (i.e., out ofthe page) and a narrower line thickness in FIGS. 6D and 6E denotesartificial muscle layers 310 shifted along the second tab axis 12 intothe background (i.e., into the page).

In FIGS. 6A-6E, the second artificial muscle layer 310B and the thirdartificial muscle layer 310C are inner artificial muscle layers. Thesecond artificial muscle layer 310B is offset from the first artificialmuscle layer 310A along the first tab axis 10 and offset from the thirdartificial muscle layer 310C along the second tab axis 12. The thirdartificial muscle layer 310C is offset from the second artificial musclelayer 310B along the second tab axis 12 and offset from the fourthartificial muscle layer 310D along the first tab axis 10. In artificialmuscle stacks 301 with increased numbers of artificial muscle layers310, this pattern may repeat allowing for a closely packed stackedarrangement of artificial muscle layers.

Referring still to FIGS. 6A-6E, the overlap between the tab portions132, 154 and expandable fluid regions 196 in adjacent artificial musclelayers 310 in the alternatingly offset arrangement of the artificialmuscle stack 301 allows an increased number artificial muscles 100 to bedisposed within a particular footprint when compared to the artificialmuscle stack 201 of FIGS. 5A-5C. Indeed, the artificial muscle stack 301maximizes the number of artificial muscles 100 that may be disposed in aparticular footprint, in both a lateral direction (i.e., along the firstand second tab axes 10, 12) and in a depth direction, maximizing thecollective actuation force per unit volume of the artificial musclestack 301. When each artificial muscle 100 actuates, the tab portions132, 154 of the electrode pair 104 close together (e.g., flatten) andthe expandable fluid region expands 196. Because the tab portions 132,154 flatten, expandable fluid regions 196 of artificial muscles 100 maybe positioned above and/or below tab portions of adjacent artificialmuscle layers 310. This allows an increased number of artificial musclesto be positioned together in a condensed block (i.e., the artificialmuscle stack 301) and operate cooperatively. Indeed, the artificialmuscle stack 301 is designed such that the artificial muscles 100 ofeach artificial muscle layer 310 are able to express their collectiveforce in an additive manner. In contrast, the coaxial alignment of theartificial muscle stack 201 of FIG. 5A limits the additive forcegenerated by each artificial muscle layer 210 because the expandablefluid regions 196 of each artificial muscle layer 210 overlap.

Referring now to FIG. 7, the artificial muscle stack 301′ is depicted.The artificial muscle stack 301′ comprises the artificial muscle stack301 of FIGS. 6A-6E with the addition of perimeter artificial muscles315. The perimeter artificial muscles 315 comprise the same structure asthe artificial muscles 100 but have fewer tab portions 132, 154 than theartificial muscles 100 of the artificial muscle stack 301′, as shown byfirst perimeter artificial muscles 315A. As shown in FIG. 7, theartificial muscles 100 of the artificial muscle stack 301′ comprise fourtab portions 132, 154 and the perimeter artificial muscles 315 compriseeither two or three tab portions 132, 154. In particular, the perimeterartificial muscles 315 may comprise edge perimeter artificial muscles316 and corner perimeter artificial muscles 318. The edge perimeterartificial muscles 316 extend along a single side of the artificialmuscle stack 301 and the corner perimeter artificial muscles 318 aredisposed at a corner of the artificial muscle stack 301 such that onetab portion of the corner perimeter artificial muscles 318 extends alongone side of the artificial muscle stack 301 and another tab of thecorner perimeter artificial muscle 318 extend along another side of theartificial muscle stack 301.

As shown in FIGS. 6A-6E, the alternating offset arrangement of theplurality of artificial muscle layers 310 of the artificial muscle stack301 creates a symmetry imbalance along the edges of the artificialmuscle stack 301. That is, due to the alternating offset arrangement,the artificial muscle layers 310 may laterally terminate at differentlocations, leaving edge gaps in the artificial muscle stack 301. Asshown in FIG. 7, the perimeter artificial muscles 315 may be used tofill these edge gaps such that each artificial muscle layer 310 of theartificial muscle stack 301′ are laterally coterminous. In someembodiments, each artificial muscle layer 310 may comprise perimeterartificial muscles 315, for example, a combination of edge perimeterartificial muscles 316 and corner perimeter artificial muscle 318 toboth balance the symmetric along the edges of the artificial musclesstack 301 and add additional actuation force to the artificial musclestack 301 without increasing the overall footprint.

Referring now to FIGS. 8A and 8B, the layered actuation structure 500 isschematically depicted. FIG. 8A schematically depicts the layeredactuation structure 500 in a non-actuated state. FIG. 8B schematicallydepicts the layered actuation structure 500 in an actuated state. Thelayered actuation structure 500 includes one or more actuation platforms502 interleaved with one or more mounting platforms 506 to form one ormore platform pairs 510. Each platform pair 510 includes a mountingplatform 506 and actuation platform 502 forming an actuation cavity 512therebetween. The one or more actuation platforms 502 each comprise acavity facing surface 504. Similarly, the one or more mounting platforms506 each comprise a cavity-facing surface 508. In each platform pair510, the cavity-facing surface 504 of the individual actuation platform502 faces the cavity-facing surface 508 of the individual mountingplatform 506. In some embodiments, the actuation platforms 502 and themounting platforms 506 each comprise a thickness of from ¼ inch to 1/32inch, for example, ¼ inch, ⅛ inch, 1/10 inch, 1/12 inch, 1/16 inch, 1/20inch, 1/24 inch, 1/28 inch, 1/32 inch, or any range having any two ofthese values as endpoints.

Referring still to FIGS. 8A and 8B, each of the platform pairs 510 isspaced from at least one adjacent one of the platform pairs 510 by atleast a cavity displacement distance 530 to provide clearance for theone or more actuation platforms 502 to move relative to the one or moremounting platforms 506 in a movement direction (e.g., the Y-directiondepicted in FIGS. 8A and 8B). Moreover, one or more artificial muscles100 are disposed in each of the actuation cavities 512 such thatactuation of the one or more artificial muscles 100, that is, expansionof the expandable fluid region 196 applies pressure to the one or moreactuation platforms 502, generating translational motion of the one ormore actuation platforms 502. While the artificial muscles 100 aredepicted in FIGS. 8A and 8B, it should be understood that the layeredactuation structure 500 may include any embodiment of an artificialmuscle described herein. In some embodiments, a single artificial muscle100 is disposed in some or all of the actuation cavities 512. In otherembodiments, a plurality of artificial muscles 100 are disposed in someor all of the actuation cavities 512. Moreover, when a plurality ofartificial muscles 100 are disposed in an actuation cavity, theplurality of artificial muscles 100 are disposed in an artificial musclestack 301 comprising a plurality of artificial muscles layers arrangedin an alternating offset arrangement, as described above with respect toFIGS. 6A-7.

In some embodiments, as shown in FIGS. 8A and 8B, the one or moreactuation platforms 502 and the one or more mounting platforms 506 eachcomprise one or more bumps 550 extending into the one or more actuationcavities 512. In particular, the bumps 550 extend outward from thecavity-facing surface 504 of the actuation platforms 502 and thecavity-facing surface 508 of the mounting platforms 506. The one or morebumps 550 are sized and positioned to overlap with the electrode region194 of at least one of the one or more artificial muscles 100 arrangedin the actuation cavities 512. In operation, when the expandable fluidregions 196 of the artificial muscles 100 expand and press against thecavity-facing surfaces 504, 508 of the actuation platform 502 and themounting platform 506, the contracted electrode regions 194 pressagainst the bump 550. In some embodiments, the bumps 550 are arranged tocorrespond with the alternating offset arrangement of the artificialmuscle stack 301. That is, the one or more bumps 550 are positioned suchthat an individual bump 550 aligns with at least one tab portion 132which is positioned in the electrode region 194 of at least oneartificial muscle 100.

Referring also to FIGS. 9 and 10, the layered actuation structure 500further includes one or more platform linking arms 520 that connect theplatform pairs 510 to one another. The platform linking arms 520 retainthe lateral positioning of platform pairs 510 (i.e., positioning in theX and Z directions), retain the spacing between the mounting platforms506 of adjacent platform pairs 510 in the movement direction (i.e., inthe Y direction) and allow for translational motion of the actuationplatforms 502 of each platform pair 510 in the movement direction. Asshown in FIGS. 8A-10, the one or more platform linking arms 520comprising a plurality of platform linking arms 520 that include atleast one actuation arm 522 coupled to the one or more actuationplatforms 502 and at least one support arm 524 coupled to the one ormore mounting platforms 506. In particular, the actuation arm 522 isrigidly coupled to each actuation platform 502 and translatably coupledto each mounting platform 506 and the support arm 524 is rigidly coupledto each mounting platform 506 and translatably coupled to each actuationplatform 502. This translatable connection may be a slideableconnection. For example, the platform linking arms 520 may comprise aplurality of notches 525 to which provide a location for connectors 526,such as screws, to connect the platform linking arms 520 to theactuation platforms 502 and the mounting platforms 506 and also allowmotion of the actuation platforms 502 during operation of the layeredactuation structure 500 while retaining a connection between theplatform linking arms 520 and the platform pairs 510. In someembodiments, the actuation platforms 502 and the mounting platforms 506may comprise screw block sections, which are thicker than the remainingportion of each platform 502, 506 and provide a connection location forthe connectors 526.

In operation, when the one or more artificial muscles 100 apply pressureto the cavity facing surfaces 504 of the one or more actuation platforms502, the actuation platforms 502 translate relative to the mountingplatforms 506 in the movement direction. That is, actuation the one ormore artificial muscles 100 disposed in at least one of the actuationcavities 512 generates a translation motion of the one or more actuationplatforms 502 along a cavity displacement distance 530. While the cavitydisplacement distance may be increased by increasing the number oflayers of artificial muscles 100 in embodiments in which artificialmuscle stacks are disposed in the actuation cavities 512, the cavitydisplacement distance 530 is not increased by increasing the number ofplatform pairs 510. However, the translation motion of an individualactuation platform 502 generates and individual cavity force, which isan additive force.

That is, when layered actuation structure 500 comprises a plurality ofactuation cavities 512, such as in the embodiments depicted in FIGS. 8Aand 8B, each individual actuation platform generates the individualcavity force such that the layered actuation structure generates amulti-cavity force. The multi-cavity force is an additive force of eachof the individual cavity forces. In some embodiments, the multi-cavityforce is 10 Newtons (N) or greater, such as 15 N or greater, 20 N orgreater, 25 N or greater, 30 N or greater, 35 N or greater, 40 N orgreater, 45 N or greater, 50 N or greater, 55 N or greater, 60 N orgreater, 65 N or greater, 70 N or greater, 75 N or greater, 80 N orgreater, 85 N or greater, 90 N or greater, 95 N or greater, 100 N orgreater, 105 N or greater, 110 N or greater, 115 N or greater, 120 N orgreater, or any range having any two of these values as endpoints.Indeed, embodiments are contemplated in which a layered actuationstructure 500 comprising a 5 cm×5 cm lateral footprint is capable ofgenerating a multi-cavity force of 80 N.

Referring still to FIGS. 8A-10, the layered actuation structure 500further comprises an actuation surface 540 configured to apply thecavity force (e.g., an individual cavity force or multi-cavity force)generated by the translational motion of the one or more actuationplatforms 502. In some embodiments, the actuation surface 540 is asurface of an actuation block 542, which may be coupled to at least oneactuation arm 522, as shown in FIGS. 8A and 8B, or coupled to anactuation platform 502 (e.g., the upward-most or endmost actuationplatform 502), as shown in FIG. 9. In other embodiments, the actuationsurface 540 may be a surface of an actuation platform 502 itself, asshown in FIG. 10.

Referring now to FIGS. 9 and 10, embodiments of the layered actuationstructure 500 are depicted. As shown in FIGS. 9 and 10, in someembodiments, the layered actuation structure 500 comprises multiplesupport arms 522 and multiple actuation arms 520. For example, thelayered actuation structure 500 may comprise a first support arm 522A, asecond support arm 522B, a first actuation arm 520A, and a secondactuation arm 520B. The first and second support arms 522A, 522B areeach coupled to the one or more mounting platforms 506 and the first andsecond actuation arms 520A, 520B are each coupled to the one or moreactuation platforms 502. The first support arm 522A and the secondsupport arm 522B are coupled to the one or more mounting platforms 506at opposite locations along an edge 507 of the one or more mountingplatforms 506. The first actuation arm 520A and the second actuation arm520B are coupled to the one or more actuation platforms 502 at oppositelocations along an edge 503 of the one or more actuation platforms 502.Furthermore, the first and second support arms 522A, 522B are positionedrelative the first and second actuation arms 520A, 520B such that anaxis extending between the first support arm 522A and the second supportarm 522B is orthogonal an axis extending between the first actuation arm520A and the second actuation arm 520B.

Referring now to FIG. 11, an actuation system 400 may be provided foroperating each individual artificial muscle 100 of the layered actuationstructure 500. The actuation system 400 may comprise a controller 50, anoperating device 46, a power supply 48, a display device 42, networkinterface hardware 44, and a communication path 41 communicativelycoupled these components.

The controller 50 comprises a processor 52 and a non-transitoryelectronic memory 54 to which various components are communicativelycoupled. In some embodiments, the processor 52 and the non-transitoryelectronic memory 54 and/or the other components are included within asingle device. In other embodiments, the processor 52 and thenon-transitory electronic memory 54 and/or the other components may bedistributed among multiple devices that are communicatively coupled. Thecontroller 50 includes non-transitory electronic memory 54 that stores aset of machine-readable instructions. The processor 52 executes themachine-readable instructions stored in the non-transitory electronicmemory 54. The non-transitory electronic memory 54 may comprise RAM,ROM, flash memories, hard drives, or any device capable of storingmachine-readable instructions such that the machine-readableinstructions can be accessed by the processor 52. Accordingly, theactuation system 400 described herein may be implemented in anyconventional computer programming language, as pre-programmed hardwareelements, or as a combination of hardware and software components. Thenon-transitory electronic memory 54 may be implemented as one memorymodule or a plurality of memory modules.

In some embodiments, the non-transitory electronic memory 54 includesinstructions for executing the functions of the actuation system 400.The instructions may include instructions for operating the layeredactuation structure 500, for example, instructions for actuating the oneor more artificial muscles 100, individually or collectively, andactuating the artificial muscle layers 210, 310, individually orcollectively.

The processor 52 may be any device capable of executing machine-readableinstructions. For example, the processor 52 may be an integratedcircuit, a microchip, a computer, or any other computing device. Thenon-transitory electronic memory 54 and the processor 52 are coupled tothe communication path 41 that provides signal interconnectivity betweenvarious components and/or modules of the actuation system 400.Accordingly, the communication path 41 may communicatively couple anynumber of processors with one another, and allow the modules coupled tothe communication path 41 to operate in a distributed computingenvironment. Specifically, each of the modules may operate as a nodethat may send and/or receive data. As used herein, the term“communicatively coupled” means that coupled components are capable ofexchanging data signals with one another such as, for example,electrical signals via conductive medium, electromagnetic signals viaair, optical signals via optical waveguides, and the like.

As schematically depicted in FIG. 11, the communication path 41communicatively couples the processor 52 and the non-transitoryelectronic memory 54 of the controller 50 with a plurality of othercomponents of the actuation system 400. For example, the actuationsystem 400 depicted in FIG. 11 includes the processor 52 and thenon-transitory electronic memory 54 communicatively coupled with theoperating device 46 and the power supply 48.

The operating device 46 allows for a user to control operation of theartificial muscles 100 of the layered actuation structure 500. In someembodiments, the operating device 46 may be a switch, toggle, button, orany combination of controls to provide user operation. The operatingdevice 46 is coupled to the communication path 41 such that thecommunication path 41 communicatively couples the operating device 46 toother modules of the actuation system 400. The operating device 46 mayprovide a user interface for receiving user instructions as to aspecific operating configuration of the layered actuation structure 500.

The power supply 48 (e.g., battery) provides power to the one or moreartificial muscles 100 of the layered actuation structure 500. In someembodiments, the power supply 48 is a rechargeable direct current powersource. It is to be understood that the power supply 48 may be a singlepower supply or battery for providing power to the one or moreartificial muscles 100 of the layered actuation structure 500. A poweradapter (not shown) may be provided and electrically coupled via awiring harness or the like for providing power to the one or moreartificial muscles 100 of the layered actuation structure 500 via thepower supply 48.

In some embodiments, the actuation system 400 also includes a displaydevice 42. The display device 42 is coupled to the communication path 41such that the communication path 41 communicatively couples the displaydevice 42 to other modules of the actuation system 400. The displaydevice 42 may be a touchscreen that, in addition to providing opticalinformation, detects the presence and location of a tactile input upon asurface of or adjacent to the display device 42. Accordingly, thedisplay device 42 may include the operating device 46 and receivemechanical input directly upon the optical output provided by thedisplay device 42.

In some embodiments, the actuation system 400 includes network interfacehardware 44 for communicatively coupling the actuation system 400 to aportable device 70 via a network 60. The portable device 70 may include,without limitation, a smartphone, a tablet, a personal media player, orany other electric device that includes wireless communicationfunctionality. It is to be appreciated that, when provided, the portabledevice 70 may serve to provide user commands to the controller 50,instead of the operating device 46. As such, a user may be able tocontrol or set a program for controlling the artificial muscles 100 ofthe layered actuation structure 500 utilizing the controls of theoperating device 46. Thus, the artificial muscles 100 of the layeredactuation structure 500 may be controlled remotely via the portabledevice 70 wirelessly communicating with the controller 50 via thenetwork 60.

It should now be understood that embodiments described herein aredirected to a layered actuation structure having one or more actuationplatforms interleaved with one or more mounting platforms formingplatform pairs. Artificial muscles are disposed in an actuation cavityof each platform pair and are expandable on demand to selectively raisethe actuation platforms. The translational motion of each of the one ormore actuation platforms generates an additive force that may beincreased by adding additional platform pairs to the layered actuationstructure. Each additional platform pair of the layered actuationstructure increases the achievable maximum force without increasing thetotal displacement that occurs during actuation. Thus, the layeredactuation structure is useful in small footprint applications,particular small lateral footprint applications.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

While particular embodiments have been illustrated and described herein,it should be understood that various other changes and modifications maybe made without departing from the scope of the claimed subject matter.Moreover, although various aspects of the claimed subject matter havebeen described herein, such aspects need not be utilized in combination.It is therefore intended that the appended claims cover all such changesand modifications that are within the scope of the claimed subjectmatter.

What is claimed is:
 1. A layered actuation structure comprising: one ormore actuation platforms interleaved with one or more mounting platformsto form one or more actuation cavities between one or more platformpairs, each platform pair comprising an individual mounting platform andan individual actuation platform; and one or more artificial musclesdisposed in each of the one or more actuation cavities, the one or moreartificial muscles comprising: a housing comprising an electrode regionand an expandable fluid region; a dielectric fluid housed within thehousing; and an electrode pair comprising a first electrode and a secondelectrode positioned in the electrode region of the housing, wherein theelectrode pair is actuatable between a non-actuated state and anactuated state such that actuation from the non-actuated state to theactuated state directs the dielectric fluid into the expandable fluidregion, expanding the expandable fluid region thereby applying pressureto the one or more actuation platforms, generating translational motionof the one or more actuation platforms.
 2. The layered actuationstructure of claim 1, wherein the one or more platform pairs comprise aplurality of platform pairs connected to one another using one or moreplatform linking arms.
 3. The layered actuation structure of claim 2,wherein the one or more platform linking arms comprise at least onesupport arm rigidly coupled each mounting platform and translatablycoupled to each actuation platform and at least one actuation armrigidly coupled to each actuation platform and translatably coupled toeach mounting platform.
 4. The layered actuation structure of claim 1,wherein: the one or more actuation platforms and the one or moremounting platforms each comprise one or more bumps extending into theone or more actuation cavities; and at least one of the one or moreartificial muscles disposed in each of the one or more actuationcavities are positioned such that the electrode region of the housing ofthe at least one of the one or more artificial muscles overlaps at leastone of the one or more bumps.
 5. The layered actuation structure ofclaim 1, wherein the one or more artificial muscles disposed in each ofthe one or more actuation cavities comprise an artificial muscle stackcomprising: a plurality of artificial muscle layers each comprising oneor more artificial muscles, wherein the one or more artificial muscleseach comprise two or more tab portions and two or more bridge portions,wherein: each of the two or more bridge portions interconnects adjacenttab portions; and at least one of the first electrode and the secondelectrode comprises a central opening positioned between the two or moretab portions and encircling the expandable fluid region; and theplurality of artificial muscle layers are arranged such that theexpandable fluid region of the one or more artificial muscles of eachartificial muscle layer overlaps at least one tab portion of one or moreartificial muscles of an adjacent artificial muscle layer.
 6. Thelayered actuation structure of claim 5, wherein adjacent artificialmuscle layers are offset from one another along one or more tab axes,each tab axis extending from a center axis of the expandable fluidregion of an individual artificial muscle of the plurality of artificialmuscle layers to an end of at least one of the two or more tab portionsof the individual artificial muscle of the plurality of artificialmuscle layers.
 7. The layered actuation structure of claim 6, whereinthe plurality of artificial muscle layers comprise at least threeartificial muscle layers and each inner artificial muscle layer isoffset a first adjacent artificial muscle layer along a first tab axisand offset a second adjacent artificial muscle layer along a second tabaxis.
 8. The layered actuation structure of claim 7, wherein the firsttab axis is orthogonal the second tab axis.
 9. The layered actuationstructure of claim 1, wherein: the first electrode and the secondelectrode each comprise two or more tab portions and two or more bridgeportions; each of the two or more bridge portions interconnects adjacenttab portions; and at least one of the first electrode and the secondelectrode comprises a central opening positioned between the two or moretab portions and encircling the expandable fluid region.
 10. The layeredactuation structure of claim 9, wherein: when the electrode pair is inthe non-actuated state, the first electrode and the second electrode arenon-parallel to one another; and when the electrode pair is in theactuated state, the first electrode and the second electrode areparallel to one another, such that the first electrode and the secondelectrode are configured to zipper toward one another and toward thecentral opening when actuated from the non-actuated state to theactuated state.
 11. The layered actuation structure of claim 9, whereinthe first electrode and the second electrode each includes two pairs oftab portions and two pairs of bridge portions, each bridge portioninterconnecting adjacent a pair of adjacent tab portions, each tabportion diametrically opposing an opposite tab portion.
 12. The layeredactuation structure of claim 1, wherein the first electrode is fixed toa first surface of the housing and the second electrode is fixed to asecond surface of the housing.
 13. A method for actuating a layeredactuation structure, the method comprising: generating a voltage using apower supply electrically coupled to an electrode pair of one or moreartificial muscles, wherein: at least one of the one or more artificialmuscles are disposed in each of one or more actuation cavities formedbetween one or more actuation platforms and one or more mountingplatforms, the one or more actuation platforms are interleaved with theone or more mounting platforms to form one or more platform pairs, eachplatform pair comprising an actuation cavity between an individualmounting platform and an individual actuation platform; each artificialmuscle comprises a housing having an electrode region and an expandablefluid region; a dielectric fluid is housed within the housing; and theelectrode pair comprises a first electrode and a second electrode and ispositioned in the electrode region of the housing; and applying thevoltage to the electrode pair of at least one artificial muscle disposedin at least one of the one or more actuation cavities, thereby actuatingthe electrode pair of the at least one artificial muscle from anon-actuated state to an actuated state such that the dielectric fluidis directed into the expandable fluid region of the at least oneartificial muscle and expands the expandable fluid region therebyapplying pressure to at least one actuation platform, generatingtranslational motion of the one or more actuation platforms.
 14. Themethod of claim 13, wherein the layered actuation structure comprises aplurality of actuation cavities and the method comprises applyingvoltage to the electrode pair of the at least one artificial muscledisposed in at least two of the plurality of actuation cavities therebygenerating a translational motion of the one or more actuation platformsalong a cavity displacement distance, the translational motiongenerating a multi cavity force at an actuation surface, wherein themulti cavity force is an additive force of an individual cavity forcegenerated by each individual actuation cavity within which at least oneartificial muscle actuates.
 15. The method of claim 14, wherein themulti cavity force is 30 N or greater.
 16. The method of claim 14,wherein the multi cavity force is 50 N or greater.
 17. The method ofclaim 13, wherein the one or more platform pairs comprise a plurality ofplatform pairs connected to one another using one or more platformlinking arms.
 18. The method of claim 17, wherein the one or moreplatform linking arms comprise at least one support arm rigidly coupledeach mounting platform and translatably coupled to each actuationplatform and at least one actuation arm rigidly coupled to eachactuation platform and translatably coupled to each mounting platform.19. The method of claim 13, wherein the one or more artificial musclesdisposed in each of the one or more actuation cavities comprise anartificial muscle stack comprising: a plurality of artificial musclelayers each comprising one or more artificial muscles, wherein the oneor more artificial muscles each comprise two or more tab portions andtwo or more bridge portions, wherein: each of the two or more bridgeportions interconnects adjacent tab portions; at least one of the firstelectrode and the second electrode comprises a central openingpositioned between the two or more tab portions and encircling theexpandable fluid region; and the plurality of artificial muscle layersare arranged such that the expandable fluid region of the one or moreartificial muscles of each artificial muscle layer overlaps at least onetab portion of one or more artificial muscles of an adjacent artificialmuscle layer.
 20. The method of claim 19, wherein adjacent artificialmuscle layers are offset from one another along one or more tab axes,each tab axis extending from a center axis of the expandable fluidregion of an individual artificial muscle of the plurality of artificialmuscle layers to an end of at least one of the two or more tab portionsof the individual artificial muscle of the plurality of artificialmuscle layers.